Foam (e.g., a polyurethane foam) may be produced, in part, by reacting an alcohol with isocyanate. Polyols may provide hydroxyl groups and/or other functional groups that are reactive with isocyanate. The particular polyol(s) selected may impact the properties and/or the processing of the resulting foam. For example, polyether type polyols may be selected to produce a flexible foam.
Polyether type polyols may be formed by an exothermic reaction of an organic oxide with an initiator having at least one active hydrogen. An initiator may be reacted with an alkylene oxide in the presence of potassium hydroxide (KOH) to form a polyol. However, since KOH has little or no molecular weight selectivity, processes (e.g., continuous processes) that use KOH may yield a mixture of polyols having a broad range of molecular weights. A polyol composition produced using KOH may contain residual KOH. It may be desirable and/or necessary to remove this KOH from the polyol in preparation for reaction with isocyanate or other processing, thereby increasing the difficulty and costs of producing a polyol. A polyol composition produced using KOH may contain unsaturated byproducts that result from the formation of unsaturated monols (e.g., allyl alcohol). In addition, using a KOH catalyst may limit the polyol functionality and/or maximum molecular weight of the finished product polyol. For example, polyol functionality may decrease as the polyol equivalent weight increases when using a KOH catalyst.
A double metal cyanide catalyst (DMC) may be used as an alternative to KOH. In a continuous process, KOH may produce polyols with an undesirably wide molecular weight distribution. A metal cyanide catalyst may be desirable in a continuous process to produce polyols with a narrower molecular weight distribution. In addition, polyol compositions produced using a DMC catalyst may not require further processing to remove residual catalyst. However, existing catalytic processes may have poor heat transfer characteristics and/or low production rates.